clement



- E. E. CLEMENT v SUBDIVIDED SERVICE SYSTEM OF RADIO BROADCASTDISTRIBUTION Sheet "ori inal Filed. un nzz, 1924 2 Sheets- Aug. 2a,1928. Re. 17,069

E. E. CLEMENT SUBDIVIDED SERVICE SYSTEM OF R ADIO BROADCAST DISTRIBUTION9x153). Filed Marbh 22, 1924 '2 sheets-s 2 I Q 7'0 /v z L004; OJC/LLITOEI Reissuecl Aug. 28, v 1928. n

UINITEDSTATEVS PATENT OFFI E."

EDWARD E. CLEMENT, or wasnmeronfnisrnrcr or COLUMBIA, ASSIGNOR no I IEDWARD r. COLLADAY, or WASHINGTON, ms'rnrc'r or COLUMBIALV a sunmvrnnnSERVICE sYsrmvr or RADIO BROADCAST nisrmnu'rroiv.

Original No. 1,522,362, dated January 6, 1925. Serial No. 701,128, filedMarch 22 reissue filed March 18, 1926. Serial No. 95,792..

My invention relates to systems of radio, broadcast distribution and hasfor itsv object the organization of a system capable of giving serviceto subscribers in regional groups, which may be related to each other bya general organization corresponding to the long distance telephoneorganization.

I attain my object by relating my subscribers in each area to one ormore local central oflices,.by means of wired circuits, which mayconveniently be telephone line circuits. Each subscriber isprovidedwith'. a

standardized form of receiving radiophone, and each central otlice isalso provided with receiving radiophones, but much more elaborateand-powerful than those at the subscribers stations. Local service, thatis to say," local broadcasting, is received by the subscriber direct,but when he desires any station except those that are listed as local,he secures a long distance connection'through his line wires to acentral oflice radio receiving set capable of picking up and receivingthe station he wants. The subscribers instrumentmay conveniently be asingletube regenerative set Wlth common battery con nections, taking allits current supply over the subscribers wired circuit. The centraloflice radio sets may conveniently be superytalker or loud speaker.

heterodynes or the equivalent thereof, capable of receiving fromdistantstations and transforming the carrier wave length so as to relayor retransmit the original modulations over the subscribers line on along care rier wave, preferably at superaudioj; frequency, such as 30 tokc. per second.

The advantages of this arrangement will be apparent on briefconsideration. A single tube set is usually sufficient to give excellentresults with local broadcasting, and by using a dynamic receiver, itiseven possible to operate therewith a moderately loud table For distancework.

the antenna or equivalent wave collector is unnecessary, and the inputside is connected through a. tuned coupler to the line circuit. The sametube detector in the subscribers y; set then receives the distantsignals on long waves, without the necessity of elaborate tuning on, thepart of the subscriber. local service, since no operators are required,a flat rate may becharged; but the long dis 5 tance service is strictlycomparable to the For the i 1924. Application for long distance. service.in the I telephone ex-'5 change,'and calls for toll charges apportionedto the amount of service rendered, as well as the investment involved.

My invention is illustrated in the accompanying drawings, in which:

Fig. 1 1s a diagram of a subscribersstation.

Fig. 2 is a connected'diagram of the central ofiice end of thesubscribers wired line circuit, showing terminal devices and switchingmeanstherefor. i Fig. 31s a dlagram showing a central ofiicesuperheterodyne receiver with its terminal switching device and anoperators supervisory circuit.

Referring to the drawings, Figs. 1, 2 3 i in Fig. 2 will u r Fig. 1represents a subscribers instrument 1 1 is a detector'tube with theusual filament 2, grid 3 and plate 4. 5 and 6 are rheostats, 7 is achoke coil, 8' is a telephone transmitter of standard type adapted to bebridged across the line wires9 and 10 by the'push button or key 11,,which however, opens as soon as pressure is removed from it. 12is thesubscribers headphone, 13 is a loop antenna for 1 local receiving, 14 is atickler loop or regenerative coil, 15 is the usual tuningcondenseracrossthe loop, 1617 is a coupler for con necting the instrument toline'for long dis-i tance receiving,- 18 and 19 .are tuning condensersfor the long distance circuit, 20 and 21 are radiofrequency choke coilsincluded in the branch of the ordinary telephone set 22,

and 23- is'a gang switch adapted to connect the instrument for eitherlong distance or local receiving to the telephone line wires 9-10.. orto disconnect it entirely therefrom,

at will. There are no batteries at the subscribers station, all energyfor all purposes being supplied over the metallic circuit 9-10,

from the telephone exchange central ofiice.

shown in Fig. y

Fig. 2 shows one telephone line 9-10 with the switching terminals in theform of spring jacks J, a line relay L, battery B, cut-oil Y .this linewith others for telephonic use, standard Western Electric No. 1switchboard cord circuits are supposed to be employed,

which however, are not shown separate herein. The line 9-10, and anynumber of other lines assumed to be taking radio service, must besupplied with centralized current. during operation of their radiophones without keeping their signal lamps S burning, this applyingtoboth local and long distance s rxjice. "For local service. no other"connection is required at the centraloflice, but for long distance,that is to say, .for receiving from) distant stations, the subscribersline must be connected with a central oflice receiving instrument suchas thatshown in Fig.3.: The

. This connection is shown in Figs. 2land as simplest form of connectionis a direct'connection fromthe line wires'9 -10,Ito the bus bars 24-25of the receiving'*instrument.

established by means of keys K' K which may be left normallyclosed,.fb'ecause radio frequency condnsers'are included in thecircuits. .In such case'the subscriber can secure long distance .service'by mer ely turningi'his own switch into. the proper position How: ever,this permanent connection would give hlm access to only onecentralofficereceiver,

' and he would be limited to the lprogram' received from stationsselectedbythe central ofice operators". In order to give hima wider v Ithe balancing local oscillator circuit 45.

choice, I 'have indicated also interchangeable switchin means.consisting of plugs cooperating with the line jacks J on one receivinginstruments. I

' [The amount of current consumedinQthe arrange'ment herein indicated atthe sub-' scrib'ers station, .using 1 99 tube, is milliamperes.

Referringto' Fig. 3, the superheterodyne.

receiver therein shown of itself and as to. the

I details of its construction, .forms no part of the present invention.It maybe replaced by any convenient, form of receiver which will giveequivalent range, ,selectivity,fandvolume of output. .As shown itcomprises as its essential elements the follow ng: antenna circuit 26,coupler'27', inputcircuit 28, provided with' the usual tuning devicesincluding condenser 29, and a load coil 30 which may be cut in oroutbymeans of a shunting switch 31, first detector tube 32, coupler '33,andthree stages of radio; frequency amplification 34:,

' 35 and 36, each including a tri-ode' tube and transformer; also alocal oscillator circuit 37 including the tube 38, and the usual coilsto connect it with the input circuit 28. This oscillator circuit istunable by means of the condenser 39 and the longwave switch 40 .to

any wave lengththrough the/usual rang'e'o'f broadcasting, as for examplefrom 200 to 600 meters inclusive. To this circuit I have added a localmodulating circuit 41, having a microphone transmitter 42, and amodulator tube 43 with the usual connections. .It is to be understoodthat thisarrangement is typical only, and may be varied withoutdeparting from the invention. The batteries A and. B for this receivingset are indicated in the upper part of the figure, and the powerconnections maybe varied, or additional batteries employed, as requiredin practice. The

,choke coil whichis usually included in the battery branch of thestandard modulator circuit is also shown for convenience at 44 in theupper part of the figure.

"In order thata continuous program may be furnished when subscribersare'connected to long distance, giving them forexample a part of theprogram from a distantsta'tion, and then without changing the tuning ortheir connections, giving them other parts originate d locally'l add'afsecond local oscillator circuit 45., having a coil 46 so related tothe coupler 27 that localoscillations in the cir cuit 46 may take theplace otthecarrier waves received from'a distant station,thusma'intaining the heterodyne effect and thefiow'fol long wavesamplified at 34c, 35 and '36. to'the subscribefisline w ires9'-1'O'a=ndsoflto his station receiver.

Local modulations may I then 'be imposed upon the long waves thustransmitted, by means of either the inodula-l tor41, or a;suitable'modulator connected "to For the purpose oftuningandsupervision, I have shown an operators receivingset 47.comprisingthe usual'elements of the tube 48. tuned input circuit 49. anda 50 by which the set may be "connected to the output circuit 51 of thes'uperheterodyne. 'lhe sa me operators set {l7 may be used withaplurality of main 1'e ?eivingsets,as indicatedby the multiplekeyhflAls0,,the output circuit 51 of each long distance receiving set may havebus'jbars 24- 25 connected'to a plurality of switchi'ng terminals' shownas multiple jacks sertion when necessary of repeaters: and'-amp'hhersinthe circuits 5243 leading to ind'i-j vidual subscriberslines.

It should particularly be observed in the present case that I have shownno second detector'in'Figf3, the out-put circuit '51' delivering acarrier wave at low or beat radio frev. quency, lhat is to say,transmission of the received and amplified waves from the rece iving setshown in Fig. 3 over the subscribers lines is at superaudio frequency,

versely, the telephonic currents or audio frequency waves, will notdisturb the radio receiving, although this is notso important, be-

bridge with these cord circuits, and in the dia-.

- ing and bypass resistances.

cause in any combined system of this type, preference must be giventelephone service.

At the subscribers station, the choke coil 7 guards the filament circuitfrom both radio and telephone audio currents while the high resistancein the plate circuit 54: of the order of 20,000 ohms) is suflicient toprevent shunt ing of the telephone apparatus at the stution 22.

Referring to Fig. 2, theplug circuit PP is typical of a long distanceradio connecting circuit, by which the subscribers line 91O through ajack J or J and a trunk jack J or J a in Fig. 3, may be connectedtoreceive any desired distant station. This cord circuit is what isknown as the standard VVeste-rn Elec tric No. 1 switchboard cordcircuit, with listenin and ringin kevs IQ-K res ectivel D b v i 7repeating coil RR, supervisory elements ss', supervisory relays r-r' andthe usual balanc- The main battery B is supposed to have its bussesconnected in gram its positive pole is shown grounded as usual.For'special radio service, however, this ground may be omitted, aseparate battery B being then employed. Since all of the batteries shownherein are at the central station, they may be combined into one, or maybe made separate units, as circumstances and good practice may dictate.In exchanges car rying a heavy radio load, it may be advisable toprovide a separate power plant, which may" conveniently be used inparallel relation to the telephone power plant,but the relation of thetwo load curves, that is the radio load and the telephone load, is suchthat only in very exceptional cases will their peaks coincide or evenapproach each other. The main telephone peaks occur approximatelybetween10 and 11 in the morning, and 2 and 3 in the atternoon, with subsidiarypeaks at one or two points between 4 and 7 grams usually come on between3 and 4 in the afternoon and after 7 in the evening. Sub sidiaryprograms peaks would be between Con-.

. tors.

p. m. The radio pro- 2 and 3m the afternoon and6 ancl'7. in the evening,with occasional concentration at other hours, as for example when aspecial speech is broadcasted from Congress, or the like. The variationsin thetelephone load are due to well established business and socialconventions but the distribution of the radio load, (or programs) is toa great extent un der the controlof those who do the broadcasting. Thediurnal variations in efliciency of wave transmission through theether'render distance receiving more effective at night, and thiscoincides with the hours of leisure of the majority of subscribers, aswell as with the low or flat portion of the telephone load curve. 7 Ingeneral therefore, it may be said that the two services will notconflict, but will sup-- plement each other according tomy system, andthis being so, furnishes reason for pre senting herein a connectingcircuitof the type shown at PP' in Fig. 2. In a great many exchanges thesame ,switchboards and the same operators may be employed to switchradio connections that are employed to switch telephoneconnections. Thecircuit P'P is therefore made convertible, by means of switch contacts5a, 55, 57 and 58. The first two of these control the connection of aradio coupler 59-60, and the other three control the continuity of theordinary cord circuit connections 61, 62 and 64 to the plug P, from thebattery B and repeating c'oil R. The conductors 6465 and'66 leading tothe plug P are left intact at all times in order to furnish operatingcurrent to the subscriber, and to supervise the connection by means ofthe lamps s, with the ancillary purpose of op-. erating the cut-offrelay G and-putting a special tone test on the multiple jacks, so thatthe line will not test busy to telephone opera- This tone test 68 iscontrolled by a switch 67, closed when the cord is in use for radio use,and opened along with the contacts 5 i.55 when in use for telephoneservice. \Vlien the. contacts 54, 55 and 67 are closedfor radio servicethe contacts 56, 57 and 58 are opened, although it has been found thatthis is not absolutely essential to good radio transmission. One windingof each coil R is left 7 between the battery B and the conductors 64 and66, and may be supplemented by a radio choke coil, if the battery B isthe same as or is connected with the main telephonebattery, the purposebeing to keep the radio waves ofi the battery busses. i

As previously pointed out, instead of being connected through-the cordcircuit P-P, the subscribers line 9-10 may be connected to thecentralofiice distant receiver of Fig. 3 by means of the circuit .52-53,provided with switches at both ends. As a matter of fact, the circuit5253, instead of being individual, may be common toa'number of lines asindi cated by the branch wires 52* and 53*, the single pair 52-53 thusbecoming an extension of the output bus. I The transmissionover the line9-40 is facilitated by turning both ends of the line, as well understoodin the art, and I therefore include a coupler 6970 and a tuningcondenser 71, the elements 70- -71 being bridged across the line by thekey K. These elements in conjunction with the corresponding elements17--19 at the subscribers station not only render the transmissionbetter, but'e'fi'ectuall'y absorb the radio waves .and block audio wavesover the line. The

' also shown a tuning condenser 72; and it is to be noted that in theoutput circuit 51 (Fig. 3) there are two fixed condensers, intended toprevent any possible short-circuiting of telephone or battery currentsthrough the secondary of the transformer :74. These may be omitted iftuning condensers are employed as at 72 in series with the coil 59.

The operation of my system thus described isas follows: 1 i

The .su'bscribers station in'Fig. 1 is shown With all parts in acondition of disuse. If the subscriber desires telephone service. heremoves his'telephone receiver from the hook and thereby signals centralthrough the parts 'L and S, as usual. A cord circuit which may be thatshown at PP, with the contacts56, 57 and 58 closed and the contacts 5155opened, is then employed,-

to answer, test," connect, ring the wanted subscriber, and superviseyasusual. If, on

the other hand the subscriber desire s'radiophone service,-'he sets hisswitch for local or'long distance, as the case may be. Assum ing that hedesires only local receiving,

and that sufficient battery current for the filament '2 may flow throughthe line without disturbing the central oflice signal or protectivedevices, he'need do nothing further.

If he desires long distance receiving however, he calls the'operator inthe usual way, either by means of his ordinary telephone set, or bymeans of the transmitter, '8 controlled by the push button 11 associatedwith the radio set. In'accordance with standard practice, distantstations will be numbered. and in response to the inquiry Number,please, the'subscriber gives the number, as for example Radio, 412,The'operator then connects him with the superheterodyne receiver of 3which can give him the station he wants, and if necessary communicatesat the. same time through an order circuit with the radio operator incharge ofthe radio receiving apparatus. As an alternative. and inaccordance with long distance practice, the'local or A operator mayanswer the call and learning it is for radio may communicate with theradio operator over an order circuit, and the radio operator will thenconnect with one of the multiple terminals of the calling subscribersline, ascertaining direct from the subscriber what station he wants,andsetting up the necessary radio connections accordingly.

This arrangement has the obvious advantage of avoiding a tie up of theoperators cords on an A board or answering positions.- This automatic inits mode. of operation. This method has also the additional advantagethat the calling and switching tothe radioboard may be simplifiedbyestablishing a conventional form of radio calling, which may be madeby" flashing line lamp S, The A operator perceiving a line lamp toflash, would knowthat the line desired long distance radio connection.and, would pass-the call to the radio operator as before stated. usinganxorder circuit. If the lamp burns steadily, it would indicate'a desirefor telephone connection, and where the subscriber is using hisinstrument for local radio receiving there would preferably be noindication at all on the lamp S. v

hat I claim is:

1. In a 'radiophone system of broadcast distribution, a central stationand lines .lead ingftherefrom to subscribers stations, radio phonereceivers at the subscribers stations arranged to be supplied withoperating current over the line, means at the central station vforsupplying current over the lines. broadcast transmitting means at thecentral station, link circuits at the central station and switchin meansassociated with .a link circuit for adapting it either to theinterconnection of subscribers lines with each other or to theconnection of said transmitting means with subscribers" line. a I

2. In a radiophone system of broadcast 1 distribution, a central stationand. subscribers stations with lines interconnecting the radio receivingsets at the subscribersstations connected with the line to takeoperating current therefrom, means at thecentral station for supplyingsaid current over the line, means for transmitting a modulated super,

' audio frequency carrier current over the lines, a receiving circuit ateach subscribers station tuned to the frequency of said carrier current,and means at eachsubscribers station for connecting the input side ofthe said 1 radio receiving set through the said carrier currentfrequency tuned receiving circuit to the line. i

3. In a radiophone system of broadcast distribution, a central stationand subscribers stations, radiophone receiving sets at the subscribersstations, an antenna at each subscribers station, means for operativelyconnecting the input circuit of the subscribers set with either theantenna or the line, and means operable upon the switching of said inputcircuit from the antenna to the line to automatically change the tuningof said receiving set from short wave lengths to long wave lengths.

4. In a radiophone system of broadcast distribution, a central stationand subscribers stations, a network of wire lines interconnecting them,radiophone receiving sets at the subscribers stations, a receivingantenna at each subscribers station, means for distributing broadcastmatter over the lines by wired radio and means at a subscribers stationfor switching the subscribers radio receiving apparatus from radio toWired radio.

5. lna radiophone system of broadcast dis-v tribution, a common batterytelephone system having subscribers stations and lines interconnectingthe same, radiophone receivers at the subscribers stations, means at asubscribers station for receiving radio broadcast on the radio receiver,means for distributing broadcast matter over the telephone lines bywired radio, and means at the subscribers station for switching thesubscribers radio receiver from radio to wired radio.

6. In a radiophone system of broadcast distribution, a central stationand lines leading therefrom to subscribers stations, radiophonereceiversat the subscribers stations arranged to be supplied with operatingcurrent over the line, broadcast transmitting means at the cen-' tralstation, link circuits at the central station for connecting said radiotransmitting means with the subscribers lines for transmission thereoverby wired radio, means for signalling the central station from thesubscribers station over the line, and means at the subcribers stationfor switching the radio receiving set from radio reception to wiredradio reception.

7. In a radiophone system of broadcast distribution, a central stationand lines leading therefrom to subscribers stations, radiophonereceivers at the subscribers stations, broadcast transmitting means atthe central station, link circuits at the central station, switchingmeans associated with a link circuit for adapting it either to theinterconnec-- ripeo tribution, a central station and subscribersstations with lines interconnecting the same, radio receiving sets atthe subscribers stations, a radio receiving antenna for each subscribersreceiving set, means for transmitting a low frequency carrier currentover the lines, a low lrequency receiving circuit at each subscribersstation tuned to the said low frequency carrier current, and means ateach subscribers station l'or connecting the input side of the saidradio receiving set to either the antenna circuit or through the lowfrequency tuned receiving circuit to the line.

9. In a radiophone system of broadcast distribution, a central stationand subscribers stations, radiophone receiving sets at the subscribersstations each comprising a thermionic tube with plate and filamentcircuits therefor connected to the line circuit for current supply, acommon source of current at the central station connected to the lineand of a suliicient voltage to operate said plate circuits thereover,voltage reducing means connected between the line and the filamentcircuit, an antenna at the subscribers station, means lor operativelyconnecting the input circuit oi the subscribers set with either theantenna or the line, and means operable upon the switching of said inputcircuit from the antenna to the line to automatically change the tuningof said receiving set from short wave lengths to long Wave lengths.

'10. In a radiophone system of broadcast distribution, a central stat onand subscribers stations, radiophone receiving sets at the subscribersstations each comprising a thermionic tube with plate and iilamentcircuits therefor connected to the line circuit for cur rent supply, acommon soin'ce of current at the central station connected to the lineand oi a sufiicient voltage to operate said plate circuit thereover,voltage reducing means connected between the line and the filamentcircuit, a receiving antenna at each subscribers station, means fordistributing broadcast matterover the lines by Wired radio,and. means ata subscribers station for switching the tem' having subscribers stationsand lines interconnecting the same, radiophone receivers at thesubscribers. stations supplied with operating current from the centralstation over the lines, means at the subscribers station for receivingradio broadcast on the radio receiver, means for distributing broadcastmatter over the telephone lines by Wired radio, and means at thesubscribers station for switching the subscribers radio receiver fromradio to wired radio. I.

In testimony whereof I hereunto atfix my signature. I

EDWARD E. CLEMENT.

